CLINICAL EPIDEMIOLOGY : RISK AND PROGNOSIS Risk Risk factors are factors associated with an increased risk of a disease that explains the causal relationship between host, agent and environmentthe occurrence of a disease. Risk factors can be divided into two, namely a) According to the changes i. Unchangeable risk factors are risk factors that cannot be changed, such as age and genetic or hereditary factors. ii. Changeable risk factors are risk factors that can be changed, such as lifestyle or diet. b) According to its stability i. Suspected risk factors are risk factors that are suspected of causing disease but do not yet have much research/scientific evidence as factors that cause disease. ii. Established risk factors are risk factors that have a lot of research/scientific evidence as factors that cause disease, such as lung cancer which can be caused by smoking. The utility of risk viz a) Prediction: Risk factors are used to predict orpredict disease occurrence. b) Cause: an increase in the incidence of a disease in people exposed to a risk factor is often considered to be the cause of the risk factor. c) Diagnosis is carried out by testing which is a way to prove the existence (positive predictive value) of a diagnostic test. Knowledge of risk can be used in the diagnosis process. d) Prevention: if a risk factor is also the cause of the disease, then its removal can be used todisease prevention, whether the mechanism of the disease is known or not Risk factor criteria according to Sir Austin Bradford Hill are used as causal criteria : a) Strength of association It is the magnitude of the causal influence in causing disease. The stronger the association, the less it may reflect the influence of other etiological factors. b) Consistency Associations will become consistent when results are replicated in studies in different settings and using different methods. When an association is causal, it is expected to produce consistent results in different studies and in different populations. c) Specificity The more accurate we are in defining the disease and its transmission, the stronger the observed associations. d) Temporality Exposure always precedes the result. If factor "A" is believed to cause disease, then it is clear that factor "A" must necessarily precede the occurrence of disease. e) Biological stages Increasing the number of exposures will increase the risk.A dose-response relationship would provide strong evidence for a causal relationship. f) Plausability The relationship between two factors must be understandable, interconnected and theoretical foundations for each factor are needed. g) Coherence The research results obtained must be in accordance with existing theory and knowledge. h) Experiment It is the concept of assessing research associations by conducting a series of experiments which is the best way to test a hypothesis, whichcan introduce selection bias and reduce confounding. i) Analogy Comparing one element with other similar elements. If a certain substance causes disease then other similar substances must have caused the same thing The same. Prognosis A condition that exists in someone who is known to have a disease and is related to the disease with the aim of predicting something that could happen to the sufferer. Prognosis describes relatively frequent events, so that it can estimate the prognosis. Incidence counts all the consequences of the disease, including death, complications, disability, suffering and so on.The natural history of a disease is the evolution or development of the course of an infectious disease in an individual over a certain time, without medical intervention/being influenced by intervention or treatment of the disease.The clinical course of the disease describes the evolution of the disease after which the sufferer comes to seek medical help and is treated in various ways which may influence the course of the event .The natural history of a disease will be influenced by the ability of the agent which can be measured by a) Infectivity is the ability of a disease agent to cause infection, which can be determined from the number of individuals who experience infection divided by the number of individuals who are exposed. b) Pathogenicity is the ability of a disease agent to cause clinical disease which is calculated from the number of clinical cases divided by the number of individuals experiencing infection. c) Virulence is the ability of a disease agent to cause death. This indicator shows the ability of an infectious agent to cause the severity of the disease.